One third of the wealthiest people in the U.K. are currently under investigation by the country's official tax collection agency, according to a report Tuesday by the country's National Audit Office (NAO).
The tax collecting HM Revenue & Customs (HMRC) launched a specialist unit in 2009 which studies the tax accounting of the U.K.'s 6,500 richest individuals. This is a group which makes up only 0.02 percent of the population and counts over £20 million ($24.5 million) worth of assets apiece.
The dedicated unit uncovered an additional £416 million of tax for collection in 2015 to 2016 on top of what was paid voluntarily by these individuals. This is a more than doubling of the £200 million secured by similar investigations four years earlier.
It was also a sum that came in far ahead of the HMRC's internal target of £250 million for the period.
Tina Riches, national tax partner at financial affairs adviser Smith & Williamson, told CNBC via telephone that the theme of tax entities keeping a closer watch was not just restricted to the U.K.
According to Riches:"Across the board all tax authorities are trying to step up a gear in terms of pursuing any taxpayer where they feel they can squeeze some extra tax out of them."